Filament winding is a process for the production of composites, often in the form of cylindrical structures. In this process, fiber rovings or filaments are coated with a resin as they are wrapped around a mold or mandrel to produce articles such as pipe, pressure bottles and tanks, storage containers, among other things. Filament winding is typically an open atmosphere process in which fibers are immersed in a bath of resin, wound around the mandrel and the mandrel is placed in an oven to cure the resin. Once the resin has cured, the mandrel is generally removed, leaving the hollow final product.
Resins which are typically used in filament winding processes include epoxies, polyesters, and vinyl-esters. Historically, polyurethanes have not generally been used in filament winding processes because polyurethane-forming systems react with water or moisture present in the air or in the winding fibers, unlike epoxies, polyesters and vinyl-esters. The reaction of polyurethane-forming systems with water produces undesirable foaming on the surface of the composite article being produced.
One method for limiting the reaction of water with the polyurethane-forming system is pre-drying the fibers to be used in producing the composite and then conditioning the fibers in a low humidity environment. This method, however, requires equipment that is quite expensive to install.
As a result, it would be desirable to provide filament winding processes and systems that use polyurethanes and that address at least some of these problems.